I've driven it for 550km so far, rarely exceeding 3000rpm (by a bit), and never driving above 80kmph. That's what the dealership told me at least.
Anyone have advice on proper break in for a car?

I have an IS350C and IS F as you may know. Don't be scared to dig in the cars butt dude, it is built for it. You don't need to floor it through every gear but step on it when you get on the high way for sure. The car needs it and so does the motor. You want to get all the small metal shavings inside the motor doing break in before 500 miles. Once you hit 500 miles, change it over to 0w-30 AMSOIL Signature Series Oil and Filter. That is what I run in both my Lexus's and change my oil ONCE A YEAR or 20,000 miles whatever comes first. I didn't have to even put in 1 quart of oil in my 625hp twin turbo IS F. It is designed NOT to break down and 100 percent synthetic is what you want. Full Synthetic is NOT 100 percent Synthetic. The government states that if your oil is at least 25 percent synthetic you can write Full Synthetic on your label. Bet you all didn't know that, but it is true. If you want to use Full Synthetic oil only use Castrol GTX, or Mobil 1 all other brands are junk straight up. I have tested them all to see what passed or not. Lucas Oil is the worst, it fails all the tests.

BTW, once I changed over to AMSOIL I gained 2.3MGP on a tank of gas which I won't complain about. The 3.5L V6 and 5.0 V8 in the IS F loves it!

Thnx for the advice, gna check the manual just in case there's something in there. Im gonna drive around 100kmph for a couple of days before going a bit faster. Nothing worse than driving 80kpmh in a convertible, feel like a grandma on a highway. The whole oil change advice is great but I don't change my own oil. I take my car to the dealership after a set amount of KM and they maintain it for me. I'm set to go there at 1000KM for engine oil change and some other stuff.